1. Field of the Invention
The present invention relates to telephone systems. It is of particular application to mobile telephone systems, but can also find application in other systems.
2. Related Art
The GSM (Global System for Mobile communications) cellular telephone system currently supports three speech coding algorithms, the 13 kbit/s xe2x80x9cfull-ratexe2x80x9d codec (coder-decoder), the 13 kbit/s xe2x80x9cenhanced full-ratexe2x80x9d codec and the 5.6 kbit/s xe2x80x9chalf-ratexe2x80x9d codec. Control programs, based on these codec algorithms, are stored in read-only memory (ROM) within the telephone and the fixed part of the network, typically in a radio base station control system. It is envisaged that improved algorithms, providing more accurate or faster coding, will be developed in the future, but if the customer is to make use of such an algorithm he has to replace his telephone by one programmed with the new codec algorithm. Conflict can arise between the customer and the network operator over who should bear the cost of such replacement.
Various proposals have been made for upgrading or modifying systems for telecommunications terminals in which an upgrade program is transmitted over the network from a network based control facility, allowing the upgrading of suitably programmable telephones. (See for example DE3721360 (Deutsche Bundesposte) and EP0459344 (Alcatel). However the upgrading program takes time to transmit, and mobile telecommunications terminals have finite memory capacity.
According to one aspect of the present invention, there is provided a method of setting up a connection between a first element and second element of a telecommunications system in which at least the first element is capable of transmitting program data to the second element for controlling the operation of the second element ; the method comprising the steps of:
exchanging data to identify the most appropriate program data to use for communication between the first and second elements,
exchanging data relating to the program data already available to each element; and
if the second element does not already have available to it the identified program data, transmitting the program data from the first element to the second element.
This arrangement ensures that program data is only transmitted if the program data is required for the connection currently being set up. This reduces the amount of data transmitted, and reduces the likelihood of memory in the second element being over-written unnecessarily. The appropriateness of program data may be determined in relation to the type of signal to be transmitted, the quality of the signal, the memory capacity of the second element, and the capabilities of any intermediate links.
In a preferred arrangement, the two elements may be a radio base station and a mobile station of a cellular mobile radio system. Alternatively they may be two telecommunications terminals, communicating with each other over a telecommunications network. The program data transmitted from one network element to the other may be configured such that it can only be used for telecommunications transactions between those two network elements.
According to another aspect, the invention provides an element of a telecommunications system having means for storing program data suitable for controlling the operation of a second element;
means for selecting the most appropriate program data to use for communication between the first and second elements; and
means for exchanging information relating to the program data already available to each element;
means for transmitting the selected program data to the second element if the second element does not already have available to it the selected program data.
According to a further aspect, the invention comprises an element of a telecommunications system capable of receiving program data for controlling its operation from another element, comprising:
means for exchanging data relating to the program data already available to each element, and for exchanging data to identify the most appropriate program data to use for communication between the elements; and
means for receiving and storing the program data from the other element if the element does not already have available to it the identified program data.
Preferably, the first and second elements each have a memory for storing program data relating to one or more modes of operation; and the method comprises the steps of:
transmitting a signal indicative of a proposed mode of operation from the first element to the second element;
detecting the initial signal at the second element;
transmitting a response signal from the second element to the first element, the response signal having a first characteristic if the memory in the second element does not contain program data for the proposed mode of operation indicated by the signal, and having a second characteristic if the memory already contains the program data;
transmitting the program data from the first element to the second element if the first characteristic is detected; and operating the elements according to the proposed mode if either the first or the second characteristic is detected.
In a preferred arrangement the method comprises an initial process for selecting the proposed mode of operation, the process comprising the steps of:
identifying the type of connection to be made;
selecting a mode of operation suitable for the said connection type, for which the first element has the necessary program data;
exchanging signals between the first element and the second element to determine what resources are available to the second element;
if the second element does not have appropriate resources for supporting the necessary program data, repeating the mode selection and signal exchange steps for further modes of operation until a mode of operation compatible with the capabilities of the second element is identified.
In one arrangement signals are initially exchanged to determine whether the second element has appropriate resources for the selected program.
Repetitions of the process may be initiated alternately from each of the two elements. This arrangement is preferred when the two elements are both telecommunications terminals, each capable of transmitting program data to the other, as it will take fewer iterations to identify the optimum program capable of operation on both elements, whichever element initially has it. The optimum program will either be a program carried by the unit with the smaller memory (which must, necessarily, fit the other memory) or, it the other unit carries a better program which can nevertheless be accommodated in the smaller memory, that better program.
When the two elements are respectively a network element (such as the controller of a radio base station), and a terminal (such as a mobile radio unit), new programs are likely to be fed into the system only from the network side of the link. It is also unnecessary in practice to allow for the possibility that the terminal has greater memory capacity than the base station control system. In this case a measure of the actual memory capacity of the smaller unit (i.e. the terminal) can be used by the larger unit (the base station control system) to identify the optimum program more quickly.
The second element may include a further memory storing further program data for use in a default mode, the processing means being operable selectively according to said program data or said further program data, in dependence on the characteristics of the signals.
The first element can also be arranged to operate in a default mode if no response to the initial radio signal is received from the second element.